In order to make further study on the electrohydrodynamic enhancement mechanism of boiling heat transfer,the bubbles images in various electric fields were obtained with a highspeed camera,and the bubble dynamic behaviors at departure were quantitatively analyzed.Experimental results show that the bubble elongates along the direction of the electric field.The bubble’s aspect ratio and deformation rate increase with the increase of electric field intensity.The electric stress acting on the bubble surface was calculated,which indicates that the bubble deformation results primarily from the effect of electric stress acting on bubble surface.The bubble becomes slender and longer along the direction of the electric field because of that the electric stress compresses the bubble in the equatorial direction and extends the bubble along the axial direction.